


Star Prince

by Mercurians



Category: Mystic Messenger (Video Game)
Genre: Enemies to Friends to Lovers, Everyone Is Magic, Fantasy space royalty AU, M/M, Yooran, Yoosung is the literal Star Prince, maybe some background SevZen
Language: English
Status: In-Progress
Published: 2017-02-26
Updated: 2017-03-02
Packaged: 2018-09-27 01:14:05
Rating: Teen And Up Audiences
Warnings: No Archive Warnings Apply
Chapters: 2
Words: 4,631
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/9943790
Author URL: https://archiveofourown.org/users/Mercurians/pseuds/Mercurians
Summary: The lights in the night sky are protected by Yoosung, the Star Prince, a magical deity and descendant of the stars themselves. Coveting the Prince's power, a lesser ruler called the Moon Lord uses his twin sons in a plot to end Yoosung's reign by force.---This is space royalty AU with a magical love story and maybe also a battle for the universe.





	1. on the moon

**Author's Note:**

> It's a short chapter to start with, but I'm finally writing the Star Prince AU!
> 
> This is going to be very different from most things I write, genre-wise and stylistically. I hope I can do the idea justice! I really, really love this AU, and I'm SO excited to show you guys what I've been planning over the past few weeks.
> 
> Big big thanks to my whole MysMe squad on Twitter~ This fic is for YOU.

There’s a kingdom tucked away on the shadowy side of the Moon, a quiet place where moon dwellers live quiet, simple lives. They travel their cobbled streets at leisurely paces. They speak in hushed voices, as though reluctant to disrupt the silence and the stillness of their perpetual night.

Though their lives may sound dreary, these people are content. They have the things that they need: food, water, comfort, community. And inspiration. There are times when these moon dwellers, like all other beings in this universe, are lucky enough to witness small miracles in the sky.

At times, all the universe stops to watch the Star Prince do his magic. A star in the sky will flicker without warning. It will disappear for just a moment before gleaming again, bursting with brilliant light, and everyone in the Moon Kingdom will turn to the sky. They watch with held breath as a constellation or a dim cluster of stars are brightened dot by dot, knowing that somewhere in the universe, the Star Prince is hard at work. He keeps the stars aglow, and thanks to that, these people feel a lightness when they look to the sky.

It’s a lightness they rely on, and one that their leader resents.

The Moon Lord lives in a castle at the center of their kingdom, a tall and jagged structure that looms like a monstrous shadow over their homes. He is an aging, white-bearded man with little power, influence, or fame. Though he runs his kingdom efficiently, the Moon Lord’s ambition is the most monumental thing about him. His sons know this well. He stands alone at the window of his high tower, but when he calls for them, they come running from whatever part of the castle they may find themselves in.

“Saeyoung!” he calls, and within minutes, both young men are entering the door to his chambers.

The Moon Lord surveys his two sons. Saeyoung walks in first, standing tall and confident as ever. He is a man with a stony face, a tight-lipped frown, and steady eyes behind gray glasses. Though at times the Moon Lord has doubted his capabilities, Saeyoung has grown into a fine young apprentice. He’s strong and quick-witted, and while he spends far too much time doting on his brother, the Moon Lord never doubts his loyalty.

Saeran, meanwhile, is a different story. The boy has always been sickly, and it shows in his frame: thin, awkward, slightly hunched over. He stands behind his brother’s shoulder, too cowardly to face his own father fully. His eyes are cast off to the side, his red hair falling into his face.

The Moon Lord frowns. “What is this?” he says, speaking with venom. “I called specifically for Saeyoung.”

Saeran shrinks, but his brother jumps in to defend him. “We assumed you’d want to see us both,” he says. Once again, doting on his brother. That nasty habit of his.

“You assumed wrong.” The Moon Lord lifts a lazy hand upward, his deep blue robe falling down his arm as he gestures toward the door. “Saeran, you are excused. This conversation has no use for you.”

Saeran nods almost imperceptibly, gives a stiff bow, and hurries out the door.

Turning back toward his window, the Moon Lord sighs. “Your brother shouldn’t feel welcome where he hasn’t been summoned.”

With his father’s eyes turned away, Saeyoung allows his shoulders to slump somewhat. He struggles to hold back a worried expression, but he manages to keep the concern hidden from his voice. “We thought that his presence was equally necessary. He and I are twins, after all.”

“You are twins, but beyond that, there is nothing equal about you.” The Moon Lord turns around, moving slowly as he steps in his long robe. “You understand that, don’t you?”

Saeyoung, having straightened his posture again, nods rigidly. “I understand,” he says, masking his guilt.

With a drawn out sigh, the Moon Lord walks to his desk. He lifts a book and a stack of papers. “I’ve been doing research on the Star Prince,” he says, setting out pages side-by-side. “Come here and let me show you what I’ve learned.”

“Yes, sir.”

 

 

 

Saeran doesn’t mind being excused from the meeting. He’s glad to be away from his father’s judgemental glare, and even more happy to miss whatever inane lecture or training session Saeyoung will have to suffer through. Still, when Saeran returns to their room, curling up in his favorite chair to gaze out his tall window at the stars, he can’t ignore the guilt and resentment weighing heavy in his stomach. He curls his legs up against his chest, the way his father often scolds him for, resting his chin on his knees. The posture gives him a little comfort.

He could try to read a book. He could nap or go for a walk. But Saeran finds himself stuck in this same place he finds himself so often, staring out at those little glowing lights that twinkle against the dark sky. Saeran hopes for a miracle—if he’s lucky, maybe he’ll catch sight of the Star Prince at work. Just looking at the starry sky is enough to set him slightly more at ease, but he hopes nonetheless.

It doesn’t happen by the time Saeyoung returns an hour later.

Once the bedroom door is shut behind him, Saeyoung groans dramatically. “You’re really lucky you missed out on this one, bro,” he says. His tone has shifted entirely, compared to his demeanor during the meeting with his father. Suddenly, Saeyoung is expressive, exaggerated, and loud.

“What did he want?” Saeran asks softly.

“Nothing important.” Saeyoung plops down on the floor beside Saeran’s chair, resting his head against the arm to join his brother in looking out the window. “Another pointless info session. You know how the old man gets.”

“Mm.” It’s all that Saeran says, but it’s enough to send off alarms in his brother’s head.

“Hey,” Saeyoung says softly. He shifts onto his knees, facing Saeran, who stares at the floor with sadness etched on his features. Saeyoung frowns. “What’s wrong? Are you upset about earlier?”

Saeran shrugs. When he answers, his voice is nearly a whisper. “He doesn’t want me... does he? You’re going to be the Moon Lord. You’re stronger and smarter. So that means I’m just....”

“Don’t say that,” Saeyoung cuts in. “Just don’t. Honestly, who cares what that old man thinks? He only cares about _me_ because he thinks I’m useful, or whatever. Trust me, you’re better off flying under his radar.”

Saeran says nothing as he stares at the floor, the crease between his eyebrows deepening.

With a tiny sigh, Saeyoung crawls around to sit in front of his brother. “Listen,” he says, his voice turning quiet and slow. “There’s plenty you’re good at, Saeran.” When he gets no response, not even a changed expression in Saeran’s distant eyes, he continues. “You know I’m going to take over soon, right? The old man’s probably got... what, ten years left, tops? He’s on the way out.”

Nothing changes. Saeran’s gaze is cast toward a corner.

“So that means I’ll be Moon Lord soon. And when I’m Moon Lord, you can be whatever you want.” Saeyoung smiles softly. “If you want to rule with me, then you’ll rule with me. We can share—you take over the light side of the moon, and I’ll take the dark half. Or if you don’t want to rule, you can do something else.”

Saeyoung glances toward the bookshelf on the other end of their room. Rows and rows of books, almost all belonging to Saeran. “You like books, right? You could be a writer. Or a librarian, here in the castle. Something like that. You could be my advisor or my assistant. You could learn a new skill, and do something with that.” He shrugs. “Anything you want, Saeran.”

Blinking slowly, Saeran sits upright and goes back to looking out the window. Saeyoung can’t tell whether or not he’s preparing to cry. Maybe his eyes are glazed over with tears, or maybe this is the sparkle that’s always present in his brother’s eyes when he’s staring at the sky like this.

“Anything at all,” Saeyoung says. “What do you want to do, Saeran?”

There is a small pause. Saeran doesn’t move at all when he finally responds.

“I just want to look at the stars.”


	2. departure

**Notes for the Chapter:**

> I'm still trying to find my footing in this fic, pacing-wise. I'm trying to make this feel faster and lighter than my regular stuff, but I worry about going TOO quickly.... But I guess at this point in the story, it's better to move faster and get to the good stuff?
> 
> Anyway here's another chapter! Special thanks to Fo for helping me with some details.

It’s a month later, and the twins know that something about this meeting is different. Saeyoung is summoned to his father’s chambers early in the day, but this time, he isn’t called from afar. The Moon Lord shows up at the door to the twins’ bedroom. He tells Saeyoung that his presence is needed and rests a hand on the young man’s shoulder as he leads him away. No acknowledgement of his other son, which hurts more than Saeran would like to admit. Rather than worry, he tries to rest in bed with a book to distract him, but the anxious thoughts won’t keep at bay. He knows that their father called Saeyoung for something important. It scares him.

The meeting lasts most of the day. An hour in, Saeran goes to the dining hall at eats breakfast alone in the long, tall-ceilinged room, a practice he’s accustomed to. He eats slowly and hunched over. When he’s finished, he cleans the dishes himself to save their servants the trouble.

Two hours in, Saeran tries to take a walk through the castle. It’s all long, dark corridors and locked rooms. He gets bored quickly. His legs tremble, and Saeran wonders whether he’s getting sick again.

Three hours in, Saeran tries to read more of his book. It’s an engrossing read on practical magic, a skill he’s only barely proficient in, but he doesn’t get very far. With the nervous thoughts circling through his head, Saeran finds it difficult to concentrate.

Four hours in, Saeran looks at the stars.

He doesn’t know how many hours pass after that. When he is awoken from his accidental slumber still curled up in his chair, it’s to Saeyoung gently shaking his shoulder and whispering his name. Saeran blinks as his eyes adjust to the dim light in their bedroom. He tries to move his legs, but finds that his muscles ache as he pulls them away from his chest.

“Saeyoung...?” he whispers, blinking slowly. The blurriness fades from his vision, and he recognizes the distressed look on his brother’s face.

“We’ve gotta talk about something,” Saeyoung says.

They go to the balcony together. Here they can see the sky stretching across the long horizon, and their hushed voices are drowned out by the wind. They stand side-by-side at the railing, facing up toward the stars, and Saeyoung is the first to speak.

“Dad wants the Star Prince’s magic,” he says.

Saeran’s eyes widen. His grip on the railing tightens. “That’s....”

“The craziest thing you’ve ever heard?” Saeyoung guesses. “Yeah, I thought the same thing.”

“Is that even possible? To take his magic?”

Saeyoung shrugs. “Who knows. Probably not, right? But he’s convinced that the Star Prince might use a magical item, and if we could steal it, he could take over the stars. He thinks it’s worth looking into, apparently.”

Saeran glances at his brother, whose eyes are still fixed on the stars. “When you said _we_ could steal it...,” he says slowly, “that means...?”

With a dry laugh, Saeyoung looks back at his brother. “Well, I guess I meant _me_. He wants me to go. As a spy.”

There is a long silence between the two, as a look of realization crosses Saeran’s face. When Saeyoung speaks again, his voice trembles for only a moment.

“I guess in his research, he found that the Star Prince has a habit of taking in orphans. We’re twenty-one now, but he thinks I could still pass as a teenager, and then I could-”

“You’re _leaving_?” Saeran cuts in abruptly. His knuckles are white, still clenching the railing. Tears well up in his eyes.

“It would only be for a couple of months. Enough time to prove the old man’s theory wrong and fly back. Assuming we can even find the Star Kingdom to begin with....” He shakes his head. “But I won’t go, if you don’t want me to. I’ll manage to convince Dad he’s wrong eventually.”

Saeran says nothing. He turns away, staring back up at the stars. Saeyoung takes this as his answer.

“Then I’ll stay,” he says, placing a hand on his brother’s shoulder. “You and I have to stick together, ri-”

“You should do what Dad wants.”

Saeyoung draws his hand back. “What?”

Turning his face away, Saeran swallows. “Dad will be mad at both of us if you stay. You should go and prove him wrong, like you said. Or if he’s not wrong....” His voice trails off.

“... You can’t possibly mean that.” Saeyoung moves around to get a better look at Saeran’s face. “You actually think we should be messing with the _stars_?”

“I don’t know. I just don’t want Dad to be upset. He’s ruthless. He- he could even accuse you of _treason_ , Saeyoung. And... this is what Lords do anyway, isn’t it?” He looks at his brother sheepishly, but something in his eyes is completely serious. “They conquer things, to advance their kingdom.”

Saeyoung’s mouth hangs open, but he doesn’t know what to say. After a moment, he realizes that Saeran is shivering, arms hugging his chest. Saeyoung rests a hand on his brother’s back. “Let’s go inside,” he says. “It’s getting cold.”

 

 

 

Saeran doesn’t back down after that. He insists the same things: that Saeyoung should go, that it’s best to follow their father’s commands, that this is what leaders should do. Saeyoung has to admit to himself that he agrees. It would be a relatively short mission, a chance to see more of the universe. Their father is difficult to negotiate with, and Saeyoung fears how he would respond to his son’s betrayal. And finally, if he’s going to be the Moon Lord someday... perhaps he needs to start thinking more ruthlessly. He doesn’t want to be bitter and power-hungry like his father. But expansion is a practical necessity, isn’t it?

Three nights later, after a dozen conversations that repeat these same points, Saeran and Saeyoung go to sleep with this impending reality weighing on their minds. Despite their age, the twins still share a room. It’s comforting to them. Saeran, plagued by nightmares from a young age, appreciates his brother’s presence when he wakes up scared and out of breath.

The dark side of the Moon is always quiet in its perpetual night, but when the castle’s staff and servants go to sleep at the end of their “day,” the stillness feels like a heavy presence itself. Saeran whispers, and Saeyoung can hear it clearly from his bed across the wide room.

“Saeyoung? Are you awake?”

“Yeah,” he answers. “What is it?”

“Do you....” Saeran inhales, exhales. “Could you get hurt? What happens if the Star Prince finds out you’re lying?”

Saeyoung shifts around to face his brother. From meters apart, their golden eyes meet in the darkness. “That won’t happen. You know I’m way too cautious about things like that.... I won’t do anything that could put me at risk.”

Saeran says nothing. His expression shifts in a way that Saeyoung can’t quite make out.

“Are you afraid of that?” Saeyoung asks. “It’s not too late for me to tell Dad I’m not going.”

Shaking his head, Saeran answers immediately. “I’m not afraid. You should do it.” He pauses. “I’ll miss you, though.”

“I’ll miss you, too,” Saeyoung says. He forces a smile. “But don’t worry. I’ll be back before you know it, Saeran. Promise.”

 

 

 

Saeyoung packs lightly for his journey. His normal attire is ornately-designed and emblazoned with the Moon Kingdom’s insignia in several places. It would give away his social standing instantly. The castle’s tailors dress him instead in a plain tunic, pants, and simple boots. (When is father leaves the room, he spends five minutes dashing around in them, enjoying the unrestricted movement.)

In his bag, Saeyoung takes only a few necessary items. He brings a small dagger, a weapon he can wield with some proficiency. He’s more comfortable with a sword or a magic staff, but the dagger won’t arouse suspicion.

Next, he brings a small journal that his father has provided him. “When you finish writing a page,” the Moon Lord explains, “the writing will disappear, and I’ll receive your message in a book of my own. I expect daily reports from you, Saeyoung.” Along with this, he is given a compass that will display his location in space at any moment. His father wants the coordinates to the Star Kingdom immediately upon Saeyoung’s landing.

Finally, Saeyoung tucks away in the front pouch a white pebble he’s kept since his childhood. One day in their youth, when Saeran was feeling uncharacteristically energetic and well enough to play outside, they found this rock in the castle’s courtyard. Its smooth, milky white surface stood out to them. The twins convinced one another that the rock fell down from the stars. Saeyoung takes this memento, knowing it has no practical purpose. In the longest period of time he’s spent apart from his twin brother, he only hopes it will bring him some comfort.

On the day of his departure, Saeyoung, Saeran, and the Moon Lord travel to the castle’s small spaceship hangar, Saeyoung dressed in his tunic and carrying his bag over his shoulder. Together, they stand in front of his tiny ship.

For a royal family, their spacecraft is somewhat shabby. Other kingdoms have more magical means of transportation, but the Moon Kingdom resorts to crude technology. It stands at about fifteen feet high, wide at the base and pointed at the top, a shape molded from dingy metal. The ship is barely large enough to hold Saeyoung, his bag, and the supply of food he’ll need for his long journey. If the Star Kingdom is located where the Moon Lord predicts, the ship should take two long weeks to get him there.

Saeyoung grimaces when he sees the ship up close, and Saeran is the only one to notice. “Will you be safe in that?” Saeran whispers.

“Saeyoung,” the Moon Lord cuts in, his voice booming. “Say your goodbyes quickly.”

The twins look at one another, suddenly lost for words. Voice caught in his throat, Saeyoung stands in front of his brother, trying to keep fear out of his expression. Instead, he opens his arms, and Saeran embraces him eagerly.

“I’ll be home soon,” Saeyoung whispers, gently ruffling his brother’s hair. Saeran stands just a half an inch shorter, but their difference in size has always felt so noticeable. “Take care of yourself, okay? Eat all of your meals. Don’t go out in the cold.”

“I’m an _adult_ , Saeyoung.” Saeran pauses, slightly regretting his annoyed reaction. “But okay. You be safe, too, all right?”

“Of course.” Saeyoung pulls back and gives his twin a confident smile. “Have a little more faith in your big brother.”

Saeran rolls his eyes, but he’s smiling, too. “Twenty minutes older. As if that makes a difference.”

The twins break apart then. Saeyoung turns to his father. He bows, but before he can speak, the Moon Lord addresses him.

“Saeyoung. This is a crucial mission, and I wouldn’t send you if I didn’t have the utmost of confidence in your capabilities _and_ your loyalty. That said, I believe it’s necessary to reiterate just how important it is that you act in accordance with your training.” He gives Saeyoung a glare that cuts straight through the young man’s confidence. “Be on your best behavior.”

“Yes, sir.” It’s all that Saeyoung says, and he turns toward the ship. Climbing the short staircase, he gives Saeran one last smile. Then he closes the metal door and disappears into the spaceship.

Saeran and the Moon Lord must exit the hangar before the ship can take off. The large double doors shut behind them, and they stand with their backs to the room, out in the empty corridor. Saeran grips the hem of his shirt in his fists. When the spaceship starts, he jumps. It’s by far the loudest sound he’s ever heard.

What is probably a few minutes of waiting feels like many hours. For a long time, the ship runs in the other room, roaring so loudly that Saeran thinks the walls of the castle might just crumble. When he takes a cautious glance at his father, the older man is unfazed. Saeran closes his eyes, praying to every god in the sky that his brother will be safe.

And then, just as suddenly as the engine started, there is an incredible “whoosh” and the sound of the spaceship disappears into the sky. And that’s that. Saeran stands up straight, feeling suddenly hollow.

His father walks away without acknowledgment. This time, he doesn’t really mind. Saeran looks up and down the hall, wondering what he’s supposed to do next, all alone for the first time in his life. After a moment of consideration, Saeran heads for his room. He’ll read a book to pass the time. Suddenly, he doesn’t really want to look at the sky.

 

 

 

Saeyoung’s journey, as expected, takes two weeks.

Two weeks of sitting in the cockpit of the ship, getting up only to stretch or grab food.

Two weeks of staring out the front window at the landscape of stars ahead of him, barely changing.

Two weeks of uneven sleep, suddenly thrust into short cycles of frequent naps, unable to rid his body of a strange drowsiness.

Two weeks of snacking, rationing, snacking, rationing, looking forward to hunger because it gives him the chance to distract himself with food.

Two weeks of flipping through a novel he found stuffed under his seat, managing to read only three or four pages at a time before sleep overtakes him again.

Two weeks of worrying about his brother.

Two weeks of worrying about the Star Prince.

Two weeks of gripping the white pebble in his pocket, feeling the smooth surface at the tips of his fingers.

Two weeks in, when the ship starts violently shaking, Saeyoung’s mind barely registers the change.

 

 

 

“Wake up.” A woman’s voice calls to Saeyoung through the darkness. It’s soft and somewhat firm at the same time. “If you can hear me, wake up.”

He stirs, and suddenly Saeyoung can feel sensation in every inch of his body. His aching head, his cheek and bare arms pressed in dirt as he lies on his stomach, the weight of his clothing and the hand rested on his shoulder. The odd lack of pain in everything below his neck. Pulling his eyes open, Saeyoung sees only a blur of yellow light.

Not the ship. Not his bedroom. He jolts onto his elbows abruptly, blinking his eyes and trying to see.

“Don’t move too suddenly.” The calm female voice tries to soothe him, but Saeyoung rolls onto his back, pulling away from her.

He adjusts the glasses sitting askew on his face and finally gets a clear look at the stranger. Short brown hair, glasses, and a yellow robe. She looks like a fairly average woman perhaps a few years older than him, but instantly, something about her strikes Saeyoung as odd in a way he can’t process. When he pulls away, she rests her hand on her knee, making no attempt to follow after him.

“You’re finally awake,” she says, exhaling softly. “Do you know what’s going on?”

 _Of course not_ , he wants to snap back at her. But his voice is stuck in his throat. Saeyoung’s vision is adjusting, and he’s beginning to take in the sight of his surroundings. Everything is so _bright_. He’s lying in dirt, but it’s shining and gold, and it stretches a few meters away to... the edge of a crater? But he turns around, and the crater is all around him, and there’s nothing beyond it, and how is that possible?

“I’ll explain everything for you,” the woman says. “My name is Jaehee, if you’re wondering. And yes, you are sitting on a piece of land floating in space.”

Saeyoung sits up fully, and she’s right. They’re seated in the center of a flat plot of dirt, and beyond the edges, he can only see darkness and stars. Realizing how close they are to an essentially bottomless ledge, Saeyoung curls up, clutching his bag.

Jaehee rises to her feet. “Can you stand?” she asks. “If not, I can carry you. It’ll be best if we move to the castle.”

“No,” Saeyoung says. His voice is finally cooperating. The sound of it is almost unfamiliar after his long journey. “No, I can do it.” With some struggle, Saeyoung pulls himself onto wobbling legs. He thinks he may fall until Jaehee rests a hand on his shoulder. He doesn’t understand how, but he feels perfectly stable the moment she does it. Saeyoung looks up at her. “There’s... uh, a castle?”

She smiles. “Take a look behind you.”

When he turns around, Saeyoung almost falls over again. This time he looks up to see dozens of other floating plots of land just like this one, each jagged and pointed at the bottom, somehow hanging as if by invisible strings in the middle of space. And at the center, a giant castle rests atop the largest plot of all. From here, it looks barely two stories tall, practically a toy, but it’s _a castle in the middle of space_. Saeyoung’s mouth hangs open. “H... how is....”

“I’ll explain everything,” Jaehee says. “For now, take my hand.”

Saeyoung doesn’t hesitate before doing as she asks. What does he have to lose, anyway?

“Now,” Jaehee explains, “I’m going to walk you over to the castle. Whether or not you’re afraid of heights, I suggest you don’t look down.”

He doesn’t even question it. When Jaehee walks forward to the ledge, he follows just a step behind. And when she steps out into space and suspends on nothing at all, Saeyoung follows. He feels his foot hit solid ground where he watches it hit empty space. Jaehee takes another step, and so does he.

And so, together, they walk in midair to the castle. They get close, and Saeyoung thinks that it might be a bit bigger than he imagined. The proportions seem less cartoonish, the windows less huge, and maybe it’s in fact three or four stories. Maybe that tower stretches higher than he thought. Maybe that tiny garden visible in the back is, in fact, a huge plot of land. Midway there, Saeyoung fully accepts that there’s some illusionary magic at play, because now the castle is towering, as large as the one at home. No, now larger, and so much more elegant. When his feet finally meet solid ground, and he’s standing with Jaehee below the castle, Saeyoung feels dizzy at how grand it seems.

“Where am I?” His words come out through a heavy exhale.

Jaehee lets go of his hand and folds hers together at her chest, smiling softly. It’s beginning to register with Saeyoung what’s so odd about her. There’s an aloofness, a kind of strange maturity behind her every expression. Everything so practiced and calm. Jaehee answers him with a lightness in her voice. “You’re at a place where many young people like you wind up. A place where you’ll be safe and cared for.” She makes a small gesture at the castle. “This is the Star Kingdom.”

If it weren’t for the throbbing headache grounding him in his own body, Saeyoung would swear he was dreaming.


End file.
